JPWO2016052310A1 - Block copolymer composition, pressure-sensitive adhesive composition, and pressure-sensitive adhesive sheet - Google Patents

Abstract

The present invention is a block copolymer composition comprising an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (a) and an aromatic vinyl-isoprene diblock copolymer (B). The ratio (MwDa / MwDb) of the weight average molecular weight MwDa of the polyisoprene block of the triblock copolymer (A) and the weight average molecular weight MwDb of the polyisoprene block of the diblock copolymer (B) is 0.5 or more. A block copolymer having an aromatic vinyl monomer unit ratio of 10 to 30% by mass, a breaking strength of less than 8 MPa, and a breaking elongation of less than 1100%. A pressure-sensitive adhesive sheet comprising a composition, a pressure-sensitive adhesive composition containing the block copolymer composition and a tackifier resin, and a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition . According to the present invention, in order to obtain an adhesive composition excellent in both adhesive performance and die cutting performance when used in an adhesive label, it has excellent initial adhesive strength at low temperature and holding power at high temperature. A block copolymer composition is provided.

Description

  The present invention is a pressure-sensitive adhesive composition having excellent initial adhesive strength at low temperature and holding power at high temperature, and excellent in both adhesive performance and die cutting performance when used for an adhesive label, and a block for obtaining the same It is related with the adhesive sheet which has an adhesive layer which consists of a copolymer composition and the said adhesive composition.

  In recent years, from the viewpoint of environmental problems, energy saving, resource saving, etc., an adhesive composition that can be hot-melt processed without using a solvent has been recommended, and styrene-isoprene as an elastomer used in such an adhesive composition. Styrene block copolymers are widely used.

The pressure-sensitive adhesive composition requires pressure-sensitive adhesive properties such as initial adhesive strength, peel adhesive strength, and holding power, and in particular, a pressure-sensitive adhesive composition excellent in initial low-temperature adhesive strength and high-temperature holding power is required. It has been. Various studies have been conducted for the purpose of improving these adhesive performances.
For example, Patent Documents 1 and 2 disclose a pressure-sensitive adhesive composition containing a styrene-isoprene-styrene block copolymer and a styrene-isoprene block copolymer.
However, although the pressure-sensitive adhesive composition described in these documents is relatively excellent in peel adhesive strength at room temperature, either the initial adhesive force at low temperature or the holding power at high temperature is insufficient. .

  On the other hand, the pressure-sensitive adhesive label is usually produced through a step of cutting a pressure-sensitive adhesive sheet adhered to a release sheet with a die according to the shape of the target pressure-sensitive adhesive label. In this step, if a pressure-sensitive adhesive composition with inferior die cutting performance is used, the pressure-sensitive adhesive sheet is not sufficiently cut, and the pressure-sensitive adhesive labels stick to each other, significantly reducing the commercial value or the pressure-sensitive adhesive composition on the die. There is a problem that adheres and adversely affects the subsequent cutting.

So far, studies have been made to improve the die cutting performance of the pressure-sensitive adhesive composition.
For example, Patent Document 3 proposes a pressure-sensitive adhesive composition containing a styrene-isoprene-styrene block copolymer and a styrene-butadiene-styrene block copolymer. Patent Document 4 discloses a pressure-sensitive adhesive composition comprising a styrene-isoprene-styrene block copolymer, a styrene-isoprene block copolymer, and a tackifier resin, and the composition has a single glass transition temperature. It is disclosed.
However, the pressure-sensitive adhesive composition described in these documents has a problem that the degree of improvement in die cutting performance is insufficient or the die cutting performance is improved, but the adhesive performance is lowered. It was not excellent in both performance.

  In order to solve this problem, Patent Document 5 discloses an aromatic vinyl-isoprene block copolymer having two or more polyaromatic vinyl blocks, an aromatic vinyl-isoprene block copolymer, and a specific weight average molecular weight. An elastomer composition is described which contains a specific proportion of polyisoprene having:

Japanese Unexamined Patent Publication No. 63-178187 JP-A 63-178188 US Pat. No. 5,290,842 WO97 / 030844 pamphlet WO2003 / 020825 pamphlet

According to the elastomer composition described in Patent Document 5, it has excellent initial adhesive strength at low temperature, peel adhesive strength at normal temperature, and holding strength at high temperature, and adhesive performance and die cutting performance when used for an adhesive label. It is said that an adhesive composition excellent in both of these can be obtained.
However, even the elastomer composition described in Patent Document 5 may not satisfy the desired adhesive performance and die cutting performance, and there is a demand for an adhesive composition having better adhesive performance and die cutting performance. The current situation is.

  The present invention has been made in view of the above circumstances, and has an initial adhesive force at a low temperature (a temperature range of 15 to 25 ° C., the same applies hereinafter), and a high temperature (a temperature range of 40 to 60 ° C., the following). In the same manner, the pressure-sensitive adhesive composition has excellent holding power when used in a pressure-sensitive adhesive label, and is excellent in both pressure-sensitive adhesive performance and die cutting performance, a block copolymer composition for obtaining this, and the pressure-sensitive adhesive. It aims at providing the adhesive sheet which has an adhesive layer which consists of an adhesive composition.

  The present inventors diligently studied to solve the above problems. As a result, in the block copolymer composition containing an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer and an aromatic vinyl-isoprene diblock copolymer, the aromatic vinyl-isoprene-aromatic vinyl tri The weight average molecular weight of the polyisoprene block of the block copolymer is smaller than the weight average molecular weight of the polyisoprene block of the aromatic vinyl-isoprene block copolymer, and the aromatic vinyl monomer occupies the entire polymer component contained According to the block copolymer composition having a specific ratio of the unit and a specific breaking strength and elongation at break, an adhesive composition having excellent adhesive performance and improved die cutting performance is obtained. As a result, the present invention has been completed.

Thus, according to the present invention, the block copolymer composition of [1] to [4], the pressure-sensitive adhesive composition of [5] and [6], and the pressure-sensitive adhesive sheet of [7] are provided.
[1] A block copolymer composition comprising an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (A) and an aromatic vinyl-isoprene diblock copolymer (B). And
(I) Ratio (Mw _Da / Mw) of the weight average molecular weight Mw _{Da of the} polyisoprene block of the triblock copolymer (A) and the weight average molecular weight Mw _Db of the polyisoprene block of the diblock copolymer (B). _Db ) is 0.5 or more and less than 1,
(Ii) The proportion of the aromatic vinyl monomer unit in the entire polymer component contained is 10 to 30% by mass,
(Iii) A block copolymer composition having a breaking strength of less than 8 MPa and a breaking elongation of less than 1100%.
[2] The triblock copolymer (A) has a weight average molecular weight of 100,000 to 250,000, and the diblock copolymer (B) has a weight average molecular weight of 100,000 to 300,000. 1] The block copolymer composition according to the above.
[3] the triblock copolymer wherein the content Ar ^a aromatic vinyl monomer unit diblock copolymer of content Ar ^b of the aromatic vinyl monomer unit of (B) of (A) The block copolymer composition according to the above [1] or [2], wherein the ratio (Ar ^a / Ar ^b ) is 1.5 or more.
[4] The triblock copolymer (A) and the diblock copolymer (B) are contained in a range of 20 to 80% by mass, respectively, according to any one of the above [1] to [3]. Block copolymer composition.

[5] A pressure-sensitive adhesive composition comprising the block copolymer composition according to any one of [1] to [4] and a tackifier resin.
[6] The pressure-sensitive adhesive composition according to [5], which is for a pressure-sensitive adhesive label,
[7] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition according to [5].

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in the initial adhesive force in low temperature, and the retention strength in high temperature, and when used for an adhesive label, it is excellent in both adhesive performance and die cutting performance, and this is obtained. A block copolymer composition is provided.

Hereinafter, the present invention will be described in detail.
1) Block Copolymer Composition The block copolymer composition of the present invention comprises an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (A) and an aromatic vinyl-isoprene block copolymer (B And a composition comprising:
(I) Ratio (Mw _Da / Mw) of the weight average molecular weight Mw _{Da of the} polyisoprene block of the triblock copolymer (A) and the weight average molecular weight Mw _Db of the polyisoprene block of the diblock copolymer (B). _Db ) is 0.5 or more and less than 1,
(Ii) The proportion of the aromatic vinyl monomer unit in the entire polymer component contained is 10 to 30% by mass,
(Iii) The breaking strength is less than 8 MPa and the breaking elongation is less than 1100%.

<Aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (A)>
The aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (A) used in the present invention (hereinafter also referred to as “triblock copolymer (A)”) is [polyaromatic vinyl block]-[poly Isoprene block]-[polyaromatic vinyl block] is a triblock copolymer.

  The polyaromatic vinyl block (hereinafter sometimes referred to as “polyaromatic vinyl block (a)”) of the triblock copolymer (A) is a polymer chain of the triblock copolymer (A). The part which contains an aromatic vinyl monomer unit as a main structural unit.

  In the polyaromatic vinyl block (a), the aromatic vinyl monomer unit content is preferably 80% by mass or more, and more preferably 100% by mass. If the aromatic vinyl monomer unit content in the polyaromatic vinyl block (a) is too small, the pressure-sensitive adhesive composition obtained may have inferior holding power at high temperatures.

  Examples of the aromatic vinyl monomer for obtaining the polyaromatic vinyl block (a) include styrene; α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, Alkyl-substituted styrenes such as ethylstyrene and p-tert-butylstyrene; halogen-substituted styrenes such as 4-chlorostyrene, 2-bromostyrene and 3,5-difluorostyrene; 4-methoxystyrene, 3,5-dimethoxystyrene Alkoxy-substituted styrenes such as; Among these, styrene and alkyl-substituted styrene are preferable, and styrene is particularly preferable from the viewpoints of excellent adhesive performance, die cutting performance, and availability.

As long as the polyaromatic vinyl block (a) is within a range that does not substantially impair the effects of the present invention, an aromatic vinyl monomer and another monomer copolymerizable with the aromatic vinyl monomer May be obtained by copolymerization.
Specific examples of other monomers copolymerizable with the aromatic vinyl monomer include conjugates such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like. A diene monomer is mentioned.

  The weight average molecular weight of the polyaromatic vinyl block (a) is preferably 5,000 to 100,000, more preferably 6,000 to 80,000, and particularly preferably 7,000 to 70,000. If the weight average molecular weight of the polyaromatic vinyl block (a) is too small, the resulting pressure-sensitive adhesive composition may have poor holding power at high temperatures, and conversely if too large, the block copolymer composition and the pressure-sensitive adhesive. There is a possibility that the melt viscosity of the composition becomes high and handling becomes difficult.

  The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyaromatic vinyl block (a) is preferably 2 or less, more preferably 1.5 or less. . When this ratio is small, a pressure-sensitive adhesive composition that is superior in holding power at high temperatures can be obtained.

  The aromatic vinyl monomer unit content in the entire triblock copolymer (A) is usually 15 to 75% by mass, preferably 17 to 60% by mass, and more preferably 20 to 50% by mass. When the content of the aromatic vinyl monomer unit is in such a range, a pressure-sensitive adhesive composition having excellent adhesive performance and die cutting performance can be obtained efficiently.

  The triblock copolymer (A) has two polyaromatic vinyl blocks as the polyaromatic vinyl block (a), but they are different even if they are the same. May be.

  The polyisoprene block (hereinafter sometimes referred to as “polyisoprene block (a)”) of the triblock copolymer (A) is mainly composed of isoprene units in the polymer chain of the triblock copolymer (A). The part contained as a structural unit. In the polyisoprene block, the isoprene unit content is preferably 80% by mass or more, and more preferably 100% by mass. If the isoprene unit content is too small, the resulting adhesive composition may have poor initial adhesive strength at low temperatures.

  The polyisoprene block (a) may be obtained by copolymerizing isoprene and another monomer copolymerizable with isoprene, as long as the effect of the present invention is not substantially inhibited. Good. Specific examples of other monomers copolymerizable with isoprene include the above aromatic vinyl monomers; 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, etc. Conjugated diene monomers other than isoprene, and the like.

  The weight average molecular weight of the polyisoprene block (a) is preferably 70,000 to 290,000, more preferably 90,000 to 240,000, and particularly preferably 100,000 to 220,000. If the weight average molecular weight of the polyisoprene block (a) is too small, the resulting pressure-sensitive adhesive composition may have poor holding power at high temperatures, and conversely if too large, the block copolymer composition and the pressure-sensitive adhesive composition. There is a possibility that the melt viscosity of the resin becomes high and handling becomes difficult.

  The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyisoprene block (a) is preferably 2 or less, and more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition that is superior in holding power at high temperatures can be obtained.

The ratio of those having a vinyl bond (—CH═CH ₂ ) among the isoprene units in the polyisoprene block (a) is not particularly limited. Usually, it is 50 mass% or less, Preferably it is 20 mass% or less, More preferably, it is 5-10 mass%. Within this range, a pressure-sensitive adhesive composition excellent in initial adhesive strength at low temperatures can be obtained.

  The weight average molecular weight of the triblock copolymer (A) is usually 80,000 to 300,000, preferably 100,000 to 250,000, more preferably 110,000 to 230,000, and particularly preferably 120,000. ~ 220,000. If this weight average molecular weight is too small, the resulting pressure-sensitive adhesive composition may be inferior in holding power at high temperatures, and if it is too large, its melt viscosity will be high and handling may be difficult.

  The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the triblock copolymer (A) is preferably 2 or less, more preferably 1.5 or less. . When this ratio is small, a pressure-sensitive adhesive composition with better holding power at high temperatures can be obtained.

  Content of the triblock copolymer (A) in the block copolymer composition of this invention is 10-90 mass% normally, Preferably it is 15-85 mass%, More preferably, it is 20-80 mass%. If this proportion is too small, the resulting pressure-sensitive adhesive composition has poor holding power at high temperatures, and conversely if it is too large, the initial adhesive strength and die cutting performance of the pressure-sensitive adhesive composition tend to be poor.

<Aromatic vinyl-isoprene diblock copolymer (B)>
The aromatic vinyl-isoprene diblock copolymer (B) used in the present invention (hereinafter also referred to as “diblock copolymer (B)”) is derived from [polyaromatic vinyl block]-[polyisoprene block]. This is a diblock copolymer.

  The polyaromatic vinyl block (hereinafter sometimes referred to as “polyaromatic vinyl block (b)”) possessed by the diblock copolymer (B) is an aromatic group in the polymer chain of the diblock copolymer (B). The part which contains a group vinyl monomer unit as a main structural unit.

  In the polyaromatic vinyl block (b), the aromatic vinyl monomer unit content is preferably 80% by mass or more, and more preferably 100% by mass. If the content of the aromatic vinyl monomer unit in the polyaromatic vinyl block is too small, the resulting adhesive composition may have poor holding power at high temperatures.

  As the aromatic vinyl monomer for obtaining the polyaromatic vinyl block (b), the same aromatic vinyl monomers for obtaining the polyaromatic vinyl block (a) as listed above can be used. Can be mentioned. Of these, styrene and alkyl-substituted styrene are preferable, and styrene is particularly preferable.

The polyaromatic vinyl block (b) is an aromatic vinyl monomer and other monomers copolymerizable with the aromatic vinyl monomer, as long as the effects of the present invention are not substantially impaired. May be obtained by copolymerization.
Other monomers copolymerizable with the aromatic vinyl monomer include conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. The body is mentioned.

  The weight average molecular weight of the polyaromatic vinyl block (b) is preferably in the range of 5,000 to 100,000, more preferably 6,000 to 80,000, particularly preferably 7,000 to 70,000. If the weight average molecular weight of the polyaromatic vinyl block (b) is too small, the resulting pressure-sensitive adhesive composition may have poor holding power at high temperatures. Conversely, if it is too large, the melt viscosity of the pressure-sensitive adhesive composition will increase. The handling may be difficult.

  The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyaromatic vinyl block (b) is preferably 2 or less, more preferably 1.5 or less. . When this ratio is small, a pressure-sensitive adhesive composition that is superior in holding power at high temperatures can be obtained.

The polyisoprene block (hereinafter sometimes referred to as “polyisoprene block (b)”) of the diblock copolymer (B) is mainly composed of isoprene units in the polymer chain of the diblock copolymer (B). The part contained as a unit.
In the polyisoprene block (b), the content of isoprene units is preferably 80% by mass or more, and more preferably 100% by mass. If the isoprene unit content is too small, the resulting adhesive composition may have poor initial adhesive strength at low temperatures.

  The polyisoprene block (b) may be a copolymer of isoprene and another monomer copolymerizable with isoprene as long as the effect of the present invention is not substantially inhibited. Other monomers copolymerizable with isoprene include the above aromatic vinyl monomers; other than isoprene such as 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene Conjugated diene monomers.

  The weight average molecular weight of the polyisoprene block (b) is preferably 70,000 to 390,000, more preferably 90,000 to 290,000, and particularly preferably 100,000 to 270,000. If the weight average molecular weight of the polyisoprene block (b) is too small, the resulting pressure-sensitive adhesive composition may have poor holding power at high temperatures, and conversely if too large, the block copolymer composition and the pressure-sensitive adhesive composition. There is a possibility that the melt viscosity of the resin becomes high and handling becomes difficult.

  The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyisoprene block (b) is preferably 2 or less, and more preferably 1.5 or less. When this ratio is small, a pressure-sensitive adhesive composition that is superior in holding power at high temperatures can be obtained.

  The content of the aromatic vinyl monomer unit in the whole diblock copolymer (B) is usually 8 to 50% by mass, preferably 10 to 40% by mass, more preferably 12 to 30% by mass. . If the content of this aromatic vinyl monomer unit is too small, the resulting adhesive composition may have poor holding power at high temperatures, and conversely if too large, the adhesive composition is initially bonded at low temperatures. The power may be inferior.

Of the isoprene units in the diblock copolymer (B), the proportion of those having a vinyl bond (—CH═CH ₂ ) is not particularly limited, and is usually 50% by mass or less, preferably 20% by mass or less, More preferably, it is 5-10 mass%. Within this range, a pressure-sensitive adhesive composition excellent in initial adhesive strength at low temperatures can be obtained.

  The weight average molecular weight of the diblock copolymer (B) is usually 80,000 to 400,000, preferably 90,000 to 350,000, more preferably 100,000 to 300,000, and particularly preferably 110,000. 000 to 280,000. If this weight average molecular weight is too small, the resulting pressure-sensitive adhesive composition tends to be inferior in holding power at high temperatures, and conversely if it is too large, the melt viscosity of the pressure-sensitive adhesive composition becomes high and handling may be difficult. is there.

  The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the diblock copolymer (B) is preferably 2 or less, and more preferably 1.5 or less. . When this ratio is small, a pressure-sensitive adhesive composition excellent in holding power at high temperatures can be obtained efficiently.

Content of the diblock copolymer (B) in a block copolymer composition is 10-90 mass% normally, Preferably it is 20-80 mass%, More preferably, it is 25-75 mass%.
When the content of the diblock copolymer (B) is in such a range, a pressure-sensitive adhesive composition that is superior in holding power at high temperature and die cutting performance can be obtained.

In the block copolymer composition of the present invention, the weight average molecular weight Mw _Da of the polyisoprene block (a) of the triblock copolymer (A) and the polyisoprene block (b) of the diblock copolymer (B). The ratio (Mw _Da / Mw _Db ) to the weight average molecular weight Mw _Db is 0.5 or more and less than 1, preferably 0.52 to 0.98, and preferably 0.55 to 0.95. Is more preferable, and 0.58 to 0.92 is even more preferable.
In the block copolymer composition of the present invention, the proportion of the aromatic vinyl monomer unit in the entire polymer component contained in the composition is 10 to 30% by mass, and 11 to 29% by mass. It is preferable that it is 12-27 mass%, and it is more preferable that it is 13-26 mass%.
Furthermore, the block copolymer composition of the present invention has a breaking strength of less than 8 MPa, preferably less than 7.8 MPa, more preferably less than 7.6 MPa, still more preferably less than 7.5 MPa, and an elongation at break of 1100. %, Preferably less than 1080%, more preferably less than 1060%, and even more preferably less than 1050%.
The block copolymer composition of the present invention is the ratio of Mw _Da to Mw _Db (Mw _Da / Mw _Db ), the ratio of aromatic vinyl monomer units in the total polymer components contained in the composition And, when the breaking strength and breaking elongation of the composition are in the ranges as described above, the initial adhesive strength at low temperature and the holding strength at high temperature are excellent, and when used for an adhesive label, An adhesive composition excellent in both die cutting performance can be obtained. In addition, the pressure-sensitive adhesive composition also has good peel adhesion strength at room temperature.

  In the block copolymer composition of the present invention, since the effects of the present invention are well expressed in a balanced manner, the weight average molecular weight of the triblock copolymer (A) is 100,000 to 250,000. The weight average molecular weight of the diblock copolymer (B) is preferably 100,000 to 300,000.

In the block copolymer composition of the present invention, the content of the aromatic vinyl monomer unit of the triblock copolymer (A) is Ar ^a , and the aromatic vinyl monomer of the diblock copolymer (B) is used. when the content of the unit was Ar ^b, the ratio of Ar ^a and ^{Ar b (Ar a / Ar b} ) is preferably 1.5 or more, more preferably 1.6 or more, 1. More preferably, it is 7-4.0.
When the ratio of Ar ^a to Ar ^b (Ar ^a / Ar ^b ) is in such a value, the initial adhesive strength at low temperature and the holding strength at high temperature are excellent. A pressure-sensitive adhesive composition excellent in both performance and die cutting performance can be obtained efficiently.
Further, as the content of the triblock copolymer (A) and the diblock copolymer (B) in the block copolymer composition of the present invention, the effects of the present invention are well expressed in a well-balanced manner, respectively. The range of 20 to 80% by mass is preferable.

  In the block copolymer composition of the present invention, since the mass ratio (A / B) of the triblock copolymer A and the diblock copolymer B expresses the effects of the present invention favorably, 10/90 to 70/30, preferably 15/85 to 60/40.

  Although the weight average molecular weight of the whole block copolymer composition of this invention is not specifically limited, Since the effect of this invention is expressed favorably, it is 150,000-300,000 normally.

<Production of triblock copolymer (A) and diblock copolymer (B)>
The manufacturing method of a triblock copolymer (A) is not specifically limited, A conventionally well-known manufacturing method is employable. For example, a method in which a polyaromatic vinyl block and a polyisoprene block are sequentially polymerized by an anion living polymerization method, and a block copolymer having a living active terminal are produced, respectively, and will be described later. A method of producing by coupling with a coupling agent can be employed.

  The manufacturing method of a diblock copolymer (B) is not specifically limited, A conventionally well-known manufacturing method is employable. For example, a method of sequentially polymerizing a polyaromatic vinyl block and a polyisoprene block by an anion living polymerization method can be employed.

  Further, the triblock copolymer (A) and the diblock copolymer (B) may be produced separately as described above, but the polymerization steps are combined into one as follows. It can also be produced as a mixture of a triblock copolymer (A) and a diblock copolymer (B) by an anion living polymerization method.

This method includes the following first to fifth steps.
(First Step) In the polymerization solvent, an aromatic vinyl monomer is polymerized using an anionic polymerization initiator to produce a polyaromatic vinyl block having a living active terminal.
(Second Step) Isoprene is polymerized from the living active end of the polyaromatic vinyl block to obtain an aromatic vinyl-isoprene diblock copolymer having a living active end.
(Third step) A part of an aromatic vinyl-isoprene diblock copolymer having an active living end and a coupling agent are reacted and coupled to each other to couple aromatic vinyl-isoprene-aromatic vinyl block copolymer A coalescence (corresponding to the component (A)) is obtained. At this time, it adjusts so that the quantity of a coupling agent reactive group may be less than 1 molar equivalent with respect to the active terminal of an aromatic vinyl-isoprene diblock copolymer.
(Fourth step) Isoprene is added to the solution obtained in the above (third step), and the remaining living active terminal and isoprene of the aromatic vinyl-isoprene diblock copolymer having a living active terminal are obtained. And react.
(Fifth Step) The living end of the aromatic vinyl-isoprene diblock copolymer is deactivated with a polymerization terminator and corresponds to the aromatic vinyl-isoprene diblock copolymer (component (B)). .)

Hereinafter, each of the first to fifth steps will be described in order.
The first step is a step of polymerizing an aromatic vinyl monomer using an anionic polymerization initiator in a polymerization solvent to produce a polyaromatic vinyl block having a living active terminal.

The polymerization solvent to be used is not particularly limited as long as it is inert to the polymerization initiator, and for example, a chain hydrocarbon solvent, a cyclic hydrocarbon solvent, or a mixed solvent thereof can be used.
Examples of chain hydrocarbon solvents include n-butane, isobutane, n-hexane, 1-butene, isobutylene, trans-2-butene, cis-2-butene, 1-pentene, trans-2-pentene, and cis-2- Examples include pentene, n-pentane, trans-2-pentane, neopentane, and mixtures thereof.
Examples of the cyclic hydrocarbon solvent include benzene, toluene, xylene, cyclohexane and the like.
Among these, since it is easy to control the polymerization temperature and the molecular weight of the polymer, it is preferable to use a mixture of a chain hydrocarbon solvent and a cyclic hydrocarbon solvent.
When a chain hydrocarbon solvent and a cyclic hydrocarbon solvent are mixed and used, the mixing ratio is a mass ratio of (chain hydrocarbon solvent) :( cyclic hydrocarbon solvent), preferably 5:95 to 50:50, more preferably 10:90 to 40:60.

  The usage-amount of a polymerization solvent is the sum total of a 1st-4th process, and is 100-1000 mass parts normally per 100 mass parts of all the monomers to be used, Preferably it is 150-400 mass parts.

  The anionic polymerization initiator is not particularly limited, and is not particularly limited as long as it is used for anionic polymerization of an aromatic vinyl monomer and isoprene, and a known one can be used. Specific examples thereof include organic monolithium initiators such as methyl lithium, n-propyl lithium, n-butyl lithium and sec-butyl lithium. Among these, n-butyl lithium is preferable. What is necessary is just to determine the usage-amount of a polymerization initiator suitably based on a conventional method so that the polymer which has a desired weight average molecular weight may be obtained.

In addition, it is preferable to perform the polymerization in the presence of a polar compound because the polymerization rate is adjusted and a polymer having a narrow molecular weight distribution can be easily produced.
The polar compound is a compound in which the molecule has electric polarity, and specifically, a compound having a relative dielectric constant measured at 25 ° C. of preferably 2.5 to 5.0.
Examples of polar compounds include aromatic ethers such as diphenyl ether and anisole; aliphatic ethers such as diethyl ether and dibutyl ether; tertiary monoamines such as trimethylamine, triethylamine and tripropylamine; N, N, N ′, N′— And tertiary polyamines such as tetramethylethylenediamine and N, N, N ′, N′-tetraethylethylenediamine; Of these, N, N, N ′, N′-tetramethylethylenediamine is preferred.

  The amount of the polar compound used is preferably in the range of 0.05 to 0.5 mol, more preferably 0.01 to 0.1 mol, with respect to 1 mol of the anionic polymerization initiator.

The second step is a step of polymerizing isoprene from the living active end of the polyaromatic vinyl block to obtain an aromatic vinyl-isoprene diblock copolymer having a living active end.
In the second step, isoprene is preferably reacted while being continuously added in order to suppress the rapid generation of reaction heat.

  In the third step, a part of the aromatic vinyl-isoprene diblock copolymer having a living active terminal is reacted with a coupling agent, and the coupled aromatic vinyl-isoprene-aromatic vinyl block copolymer is reacted. This is a step of forming a coalescence (corresponding to the triblock copolymer (A)).

  The coupling agent is a compound having two sites that react with the living active end of the polymer molecule and bind to the polymer molecule.

  Examples of the bifunctional coupling agent having two reaction sites include bifunctional halogenated silanes such as dichlorosilane, monomethyldichlorosilane, and dimethyldichlorosilane; bifunctional alkoxysilanes such as diphenyldimethoxysilane and diphenyldiethoxysilane; Difunctional halogenated alkanes such as dichloroethane, dibromoethane, methylene chloride, dibromomethane; bifunctional such as dichlorotin, monomethyldichlorotin, dimethyldichlorotin, monoethyldichlorotin, diethyldichlorotin, monobutyldichlorotin, dibutyldichlorotin Tin halides; benzoic acid, CO, 2-chloropropene and the like. Of these, dimethyldichlorosilane is preferred. The amount of the coupling agent used is such that the amount of the aromatic vinyl-isoprene-aromatic vinyl block copolymer (corresponding to the triblock copolymer (A)) obtained by coupling is in a desired range. It may be determined appropriately.

The fourth step is a step of reacting the rest of the living active terminal of the aromatic vinyl-isoprene diblock copolymer with isoprene.
When isoprene is added, the polyisoprene chain extends from the end of the aromatic vinyl-isoprene diblock copolymer having an active end that remains without reacting with the coupling agent. Thereby, the weight average molecular weight of the polyisoprene block of the diblock copolymer (B) can be made larger than the weight average molecular weight of the polyisoprene block of the triblock copolymer (A).

  In the fifth step, the remainder of the living active terminal of the aromatic vinyl-isoprene diblock copolymer is deactivated with a polymerization terminator, and the aromatic vinyl-isoprene diblock copolymer (diblock copolymer) is obtained. (Corresponding to (B)).

  As the polymerization terminator, those usually used in anionic living polymerization can be used. Specifically, water; alcohols such as methyl alcohol and ethyl alcohol; inorganic acids such as hydrochloric acid; and organic acids such as acetic acid; monofunctional silane compounds such as chlorotrimethylsilane;

By the above method, the solution containing the mixture of a triblock copolymer (A) and a diblock copolymer (B) is obtained. You may add antioxidant to this solution as needed.
Thereafter, the polymer is separated from the solution by a known polymer separation method such as steam stripping, and the obtained polymer is dried to obtain a triblock copolymer (A) and a diblock copolymer (B ) Is obtained.

When a mixture of the triblock copolymer (A) and the diblock copolymer (B) is produced by the above method, the total amount of the triblock copolymer (A) and the diblock copolymer (B) is determined. The abundance ratio of the triblock copolymer (A) is usually 10% by mass or more, preferably 20% by mass or more, particularly preferably 25% by mass or more, and usually 60% by mass or less. If this ratio is within this range, when the block copolymer composition of the present invention is produced, the block copolymer having a preferred composition can be prepared without adding the separately produced triblock copolymer (A). A combined composition can be obtained.
The ratio of the triblock copolymer (A) to the total amount of the triblock copolymer (A) and the diblock copolymer (B) can be adjusted by the amount of the coupling agent used.

  The block copolymer composition of the present invention may contain a desired amount of conventionally known antioxidants, ultraviolet absorbers, antiblocking agents, fillers, pigments and the like.

  The manufacturing method of the block copolymer composition of this invention is not specifically limited. For example, the method of knead | mixing and manufacturing the triblock copolymer (A) and the diblock copolymer (B) which were manufactured or obtained separately in a predetermined ratio, a triblock copolymer (A), and a diblock, respectively The copolymer (B) is mixed at a predetermined ratio in the state of a solution, the polymer is separated by a known method, dried and produced, and the triblock copolymer (A ) And a diblock copolymer (B) mixture can be used as a polymer component.

2) Adhesive composition The adhesive composition of this invention contains the block copolymer composition of this invention, and tackifying resin.
The tackifying resin is not particularly limited, and conventionally known natural resin-based tackifying resins, synthetic resin-based tackifying resins, and the like used in the pressure-sensitive adhesive composition can be used.

Examples of natural resin-based tackifier resins include rosin resins and terpene resins.
Examples of rosin resins include rosins such as gum rosin, tall rosin and wood rosin; modified rosins such as hydrogenated rosin, disproportionated rosin and polymerized rosin; rosin esters such as glycerin ester and pentaerythritol ester of modified rosin Is done.
Examples of terpene resins include terpene resins such as α-pinene, β-pinene, and dipentene (limonene), as well as aromatic modified terpene resins, hydrogenated terpene resins, terpene phenol resins, and the like.

Synthetic resin tackifying resins are roughly classified into polymerization tackifying resins and condensation tackifying resins. Polymeric tackifier resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, copolymerized (C5-C9) petroleum resins, hydrogenated petroleum resins, and alicyclic petroleum. Petroleum resins such as resins; coumarone / indene resins; styrene-based and substituted styrene-based pure monomer-based petroleum resins. Examples of the condensation tackifier include phenolic resins such as alkylphenol resins and rosin-modified phenolic resins, and xylene resins.
Among these, petroleum resins are preferable, copolymer petroleum resins having a copolymerization amount of aliphatic petroleum resin and aromatic monomer of 30% by mass or less are more preferable, and copolymerization of aromatic monomers. Copolymer petroleum resins having an amount of 25% by mass or less are particularly preferable.

  The compounding quantity of tackifying resin is 10-500 mass parts normally per 100 mass parts of block copolymer compositions of this invention, Preferably it is 50-350 mass parts, More preferably, it is 70-250 mass parts.

  The pressure-sensitive adhesive composition of the present invention may contain a desired amount of an elastomer other than the block copolymers (A) and (B) as long as the effects of the present invention are not substantially inhibited.

  Examples of the other elastomer include styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, polybutadiene, polyisoprene, and natural rubber. Illustrated.

  The pressure-sensitive adhesive composition of the present invention may contain other compounding agents such as a softening agent, an antioxidant, an ultraviolet absorber and a filler, if necessary.

  Examples of the softening agent that can be used include extension oils such as aromatic process oils, paraffinic process oils, and naphthenic process oils; liquid polymers such as polybutenes and polyisobutylenes; among these, paraffinic process oils and Extension oils such as naphthenic process oils are preferred.

  The amount of the softener used is preferably 5 to 500 parts by mass, more preferably 10 to 300 parts by mass, and particularly preferably 10 to 150 parts by mass per 100 parts by mass of the block copolymer composition of the present invention. If the amount of the softening agent is too small, the pressure-sensitive adhesive composition has a high melt viscosity and tends to be difficult to handle. Conversely, if the amount is too large, the softening agent tends to bleed.

  Examples of the antioxidant include 2,6-di-tert-butyl-p-cresol and pentaerythrityl tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]. Hindered phenol compounds; thiodicarboxylate esters such as dilauryl thiodipropionate and distearyl thiodipropionate; tris (nonylphenyl) phosphite and 4,4′-butylidene-bis (3-methyl-6) And phosphites such as -tert-butylphenyl) ditridecyl phosphite. These amounts used may be appropriately determined according to the characteristics of the respective antioxidants and the characteristics required for the pressure-sensitive adhesive composition to be obtained.

The pressure-sensitive adhesive composition of the present invention can be produced by mixing the block copolymer composition of the present invention, a tackifier resin, and, if desired, other compounding agents.
The manufacturing method is not particularly limited, and a conventionally known method can be employed. For example, a method of melting and kneading each component at a high temperature of about 160 to 180 ° C. under a nitrogen atmosphere can be employed.

  The pressure-sensitive adhesive composition of the present invention obtained as described above is excellent in initial adhesive strength at low temperature and holding power at high temperature, and is excellent in both pressure-sensitive adhesive performance and die cutting performance when used for pressure-sensitive adhesive labels. It is a thing. Further, the pressure-sensitive adhesive composition of the present invention has good peel adhesion strength at room temperature.

3) Adhesive sheet The adhesive sheet of this invention has an adhesive layer which consists of an adhesive composition of this invention.
The pressure-sensitive adhesive layer can be usually formed by applying the pressure-sensitive adhesive composition of the present invention on a support and drying it.

  The support to be used is not particularly limited. For example, paper such as kraft paper, Japanese paper, fine paper and synthetic paper; cloth such as cotton cloth, soft cloth and polyester cloth; cellophane film, polyvinyl chloride film, polypropylene film And resin films such as polyethylene film; metal foils such as aluminum foil and copper foil; nonwoven fabrics such as polyester nonwoven fabric and rayon nonwoven fabric.

  These supports may have a surface subjected to a corona discharge treatment or a primary coating agent applied in advance.

  A coating method is not particularly limited, and a conventionally known method can be employed. For example, the pressure-sensitive adhesive composition of the present invention is dissolved in a suitable organic solvent to adjust the viscosity, the resulting coating solution is applied, the pressure-sensitive adhesive composition is heated and melted, and the emulsifier is added. It is possible to employ a method in which the pressure-sensitive adhesive composition is dispersed in water to prepare an emulsion, and this emulsion is applied.

  Examples of the organic solvent for dissolving the pressure-sensitive adhesive composition include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; and halides thereof.

An adhesive layer can be formed by apply | coating the coating liquid containing an adhesive composition on a support body, and drying.
Since the obtained pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer is excellent in pressure-sensitive adhesive properties and die cutting performance.
The thickness of the pressure-sensitive adhesive layer is usually 10 μm to 100 μm, preferably 20 μm to 70 μm.

  The pressure-sensitive adhesive sheet of the present invention may be cut or punched into an appropriate shape according to the intended use. Furthermore, the adhesive layer which the adhesive sheet of this invention has is not limited to what was formed continuously. For example, it may be a pressure-sensitive adhesive layer formed in a regular or random pattern such as a dot shape or a stripe shape.

  In the pressure-sensitive adhesive sheet of the present invention, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention is fixedly provided on at least one surface of the support, that is, without intention to separate the pressure-sensitive adhesive layer from the support. It is. The concept of the adhesive sheet here includes an adhesive tape, an adhesive film, an adhesive label, and the like. Since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention having excellent die cutting performance, it is particularly suitable for use in pressure-sensitive adhesive labels used by die cutting.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, unless otherwise indicated, the part and% in each example are a mass reference | standard.

Various measurements were performed according to the following methods.
[Block copolymer composition and weight average molecular weight of each block copolymer in the block copolymer composition]
The molecular weight was calculated in terms of polystyrene by high performance liquid chromatography using tetrahydrofuran as a carrier at a flow rate of 0.35 mL / min. The device is HLC8220 (manufactured by Tosoh Corporation), the column is a combination of three Shodex (registered trademark) [manufactured by Showa Denko KK, KF-404HQ] (column temperature 40 ° C.), the detector is a differential refractometer and ultraviolet detector The molecular weight calibration used was carried out with 12 points of standard polystyrene (5 to 3 million) manufactured by Polymer Laboratories.

[Content of each block copolymer in the block copolymer composition]
It calculated | required from the area ratio of the peak corresponding to each block copolymer of the chart obtained by said high performance liquid chromatography.

[Weight average molecular weight of styrene polymer block of block copolymer]
Rubber Chem. Technol. 45, 1295 (1972), the block copolymer was reacted with ozone and reduced with lithium aluminum hydride to decompose the isoprene polymer block of the block copolymer. Specifically, the procedure was as follows. That is, 300 mg of the sample was dissolved in a reaction vessel containing 100 mL of dichloromethane treated with molecular sieves. After putting this reaction container into a cooling tank and making it -25 degreeC, the ozone generated with the ozone generator was introduce | transduced, supplying oxygen at the flow volume of 170 mL / min. After 30 minutes from the start of the reaction, it was confirmed that the reaction was completed by introducing a gas flowing out of the reaction vessel into the potassium iodide aqueous solution. The obtained reaction solution is designated as reaction solution 1.
Next, 50 mL of diethyl ether and 470 mg of lithium aluminum hydride were charged into another reaction vessel whose interior was purged with nitrogen, and the reaction solution 1 was slowly dropped into this reaction vessel while cooling the reaction vessel with ice water. Then, the reaction vessel was placed in a water bath, gradually heated, and refluxed at 40 ° C. for 30 minutes. After completion of the reaction, dilute hydrochloric acid was added dropwise to the reaction vessel little by little while stirring the solution, and the addition was continued until almost no hydrogen generation was observed. The obtained reaction solution is designated as reaction solution 2. The solid product produced in the reaction solution 2 was filtered off, 100 mL of diethyl ether was added to the filtered solid product, the whole volume was stirred for 10 minutes, and then filtered to obtain an extract. The extract and the filtrate obtained by filtration were combined, and the solvent was distilled off from the combined solution to obtain a solid sample.
For the sample thus obtained, the weight average molecular weight was measured according to the above-described method for measuring the weight average molecular weight, and the value was taken as the weight average molecular weight of the styrene polymer block.

[Weight average molecular weight of block copolymer isoprene polymer block]
Subtract the weight average molecular weight of the corresponding styrene polymer block from the weight average molecular weight of the block copolymer obtained as described above, and obtain the weight average molecular weight of the isoprene polymer block based on the calculated value. It was.

[Styrene unit content of block copolymer]
It calculated | required based on the detection intensity ratio of a differential refractometer and an ultraviolet detector in the measurement of said high performance liquid chromatography. In addition, the copolymer which has different styrene unit content was prepared previously, and the analytical curve was created using them.

[Styrene unit content of block copolymer composition (whole)]
^It calculated | required based on the measurement of < ¹ > H-NMR.

[Tensile properties of block copolymer composition]
Using a 1 mm thick sheet of block copolymer press-molded at 170 ° C., the breaking strength and breaking elongation were measured by a method according to JIS K 6251. As the dumbbell shape, JIS-7113-2 (1/2 size) was used. The smaller the value of both breaking strength and breaking elongation, the better the die-cut property of the label.

[Initial adhesive strength of pressure-sensitive adhesive composition for labels]
Using a 25 mm wide adhesive tape as a sample and a hard polyethylene (HDPE) plate as an adherend, loop speed (N / 25 mm) at a test speed of 1000 mm / min, an adhesive part of 25 × 25 mm, and a temperature of 23 ° C. Evaluation was performed using a tensile tester. The larger the value, the better the initial adhesive strength.

[Retention force of pressure-sensitive adhesive composition for labels]
The sample is an adhesive tape having a width of 10 mm, a mirror surface SUS plate is used as the adherend, and the adhesive part is 10 × 25 mm and the load is 3.92 according to PSTC-6 (the holding force test method by the US adhesive tape committee). The holding power was evaluated by the time (minutes) until peeling at × 10 ⁴ Pa and a temperature of 50 ° C. The larger the value, the better the holding power.

[Example 1]
To the pressure resistant reactor, 23.3 kg of cyclohexane, 4.88 mmol of N, N, N ′, N′-tetramethylethylenediamine (hereinafter referred to as “TMEDA”) and 2.1 kg of styrene I were added. While stirring the whole volume at 40 ° C., 162.73 mmol of n-butyllithium was added, the reaction solution was heated to 50 ° C., and a polymerization reaction was carried out for 1 hour. The polymerization conversion of styrene at this time was 100%. Subsequently, 7.0 kg of isoprene I was continuously added over 1 hour while maintaining the temperature of the reaction solution at 50 to 60 ° C. After the addition of isoprene was completed, the polymerization reaction was further performed for 1 hour. At this time, the polymerization conversion rate of isoprene was 100%.
Next, 43.94 mmol of dimethyldichlorosilane (bifunctional coupling agent) was added as a coupling agent to the obtained reaction solution, and the coupling reaction was carried out for 2 hours. Aromatic vinyl-isoprene-aromatic vinyl tri A block copolymer (A) was formed. Thereafter, 4.0 kg of isoprene II was continuously added over 1 hour while maintaining the temperature of the reaction solution at 50 to 60 ° C. After the addition of isoprene was completed, a polymerization reaction was further performed for 1 hour to form an aromatic vinyl-isoprene diblock copolymer (B). At this time, the polymerization conversion rate of isoprene was 100%. Thereafter, 244.1 mmol of methanol was added as a polymerization terminator to stop the reaction. The amount of each reagent used in the reaction is summarized in Table 1.
To the reaction solution 100 parts (containing 36 parts of the polymer component) obtained as described above, 0.36 part of 2,6-di-tert-butyl-p-cresol was added as an antioxidant and mixed. The mixed solution was added dropwise to warm water heated to 85 to 95 ° C. little by little to volatilize the solvent to obtain a precipitate. The obtained precipitate was pulverized and dried with hot air at 85 ° C., thereby recovering the composition of Example 1 (block copolymer composition).
In addition, a part of the obtained reaction solution is taken out, the weight average molecular weight of each block copolymer contained, the content of each block copolymer in the block copolymer composition, the content of each block copolymer Weight average molecular weight of styrene polymer block, weight average molecular weight of isoprene polymer block of each block copolymer, styrene unit content of each block copolymer, styrene unit content of block copolymer composition (whole) Asked.
Moreover, the obtained block copolymer composition was press-molded at 170 ° C. to prepare a sheet having a thickness of 1 mm, and the tensile properties were evaluated. These values are shown in Table 2.

[Examples 2-3]
The compositions of Examples 2 and 3 were recovered in the same manner as in Example 1 except that the amounts of styrene, n-butyllithium, TMEDA, isoprene, dimethyldichlorosilane, and methanol were changed as shown in Table 1, respectively. did. About the composition of Example 2 and 3, the same measurement as Example 1 was performed. The results are shown in Table 2.

[Comparative Example 1]
To a pressure-resistant reactor, 23.3 kg of cyclohexane, 3.75 mmol of TMEDA and 1.7 kg of styrene I were added, and while stirring at 40 ° C., 125.0 mmol of n-butyllithium was added and the temperature was raised to 50 ° C. Polymerization was conducted for 1 hour while warming. The polymerization conversion of styrene was 100%. Subsequently, 8.4 kg of isoprene I was continuously added to the reactor over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After completing the addition of isoprene, polymerization was continued for an additional hour. The polymerization conversion rate of isoprene was 100%. Next, 27.50 mmol of dimethyldichlorosilane was added as a coupling agent to conduct a coupling reaction for 2 hours, and then 187.5 mmol of methanol was added to the reactor as a polymerization terminator to stop the reaction. The amount of each reagent used in the reaction is summarized in Table 1. A part of the obtained reaction solution was taken out and subjected to the same measurement as in Example 1. These values are shown in Table 2. To 100 parts of the reaction solution (containing 30 parts of the polymer component) thus obtained, 0.3 part of 2,6-di-tert-butyl-p-cresol was added as an antioxidant and mixed. The mixed solution was added dropwise to warm water heated to 85 to 95 ° C. little by little to volatilize the solvent to obtain a precipitate. The precipitate was pulverized and dried with hot air at 85 ° C. The composition was recovered. About the obtained composition, it carried out similarly to Example 1, and evaluated the tensile physical property. The evaluation results are shown in Table 2.

[Comparative Example 2]
To a pressure-resistant reactor, 23.3 kg of cyclohexane, 2.50 mmol of TMEDA and 0.9 kg of styrene I were added. While stirring at 40 ° C., 83.33 mmol of n-butyllithium was added and the temperature was raised to 50 ° C. Polymerization was conducted for 1 hour while warming. The polymerization conversion of styrene was 100%. Subsequently, 8.2 kg of isoprene I was continuously added to the reactor over 1 hour while controlling the temperature so as to maintain 50 to 60 ° C. After completing the addition of isoprene, polymerization was continued for an additional hour. The polymerization conversion rate of isoprene was 100%. Next, 0.9 kg of styrene II was further added to carry out the reaction, and then 125.0 mmol of methanol as a polymerization terminator was added to the reactor to stop the reaction. The amount of each reagent used in the reaction is summarized in Table 1. A part of the obtained reaction solution was taken out and subjected to the same measurement as in Example 1. These values are shown in Table 2. To 100 parts of the reaction solution (containing 30 parts of the polymer component) thus obtained, 0.3 part of 2,6-di-tert-butyl-p-cresol was added as an antioxidant and mixed. The mixed solution was added dropwise to warm water heated to 85 to 95 ° C. little by little to volatilize the solvent to obtain a precipitate. The precipitate was pulverized and dried with hot air at 85 ° C. The composition was recovered. About the obtained composition, it carried out similarly to Example 1, and evaluated the tensile physical property. The results are shown in Table 2.

[Comparative Example 3-1]
The composition of Comparative Example 3-1 was recovered in the same manner as Comparative Example 1 except that the amounts of styrene, n-butyllithium, TMEDA, isoprene, dimethyldichlorosilane and methanol were changed as shown in Table 1, respectively. did. About the composition of Comparative Example 3-1, the same measurement as Example 1 was performed after mixing with the composition of Comparative Example 3-2. The results are shown in Table 2.

[Comparative Example 3-2]
To a pressure-resistant reactor, 23.3 kg of cyclohexane and 12.50 mmol of TMEDA were added, and while stirring at 40 ° C, 416.67 mmol of n-butyllithium was added, and isoprene was maintained so as to maintain 50 ° C to 60 ° C. 10.0 kg of I was added continuously over 1 hour. After completing the addition of isoprene, polymerization was continued for an additional hour to form a polyisoprene homopolymer. The polymerization conversion rate of isoprene was 100%. Thereafter, 625.01 mmol of methanol was added as a polymerization terminator and mixed well to stop the reaction. The amount of each reagent used in the reaction is summarized in Table 1. To 100 parts of the reaction solution (containing 30 parts of the polymer component) thus obtained, 0.3 part of 2,6-di-tert-butyl-p-cresol was added as an antioxidant and mixed. The composition solution of Comparative Example 3-2 (polyisoprene) was recovered by vacuum drying the mixed solution at 60 ° C. About the composition of Comparative Example 3-2, the same measurement as Example 1 was performed after mixing with the composition of Comparative Example 3-1. The results are shown in Table 2. In Table 2, the results obtained by using the composition obtained by mixing the composition of Comparative Example 3-1 (70 parts) and the composition of Comparative Example 3-2 (30 parts) are shown. This is shown as Comparative Example 3.

Example 4
100 parts of the composition obtained in Example 1 was put into a stirring blade type kneader, and a tackifier resin (trade name “Quinton (registered trademark) D100”, aliphatic aromatic copolymer hydrocarbon resin, Japan 150 parts of Zeon Co., Ltd., 50 parts of softener (trade name “Sunpure N90”, naphthenic process oil, manufactured by Nippon Kosan Co., Ltd.) and antioxidant (trade name “Irganox (registered trademark) 1010”, BASF Corporation (Product made) After adding 3 parts and replacing the system with nitrogen gas, the pressure-sensitive adhesive composition for Example 4 was prepared by kneading at 160 to 180 ° C. for 1 hour. The obtained pressure-sensitive adhesive composition for labels was applied to a polyester film having a thickness of 25 μm, and the samples obtained thereby were evaluated for initial adhesive force and holding power. These results are shown in Table 3.

[Examples 5-6, Comparative Examples 4-6]
The adhesive compositions for labels of Examples 5 to 6 and Comparative Examples 4 to 6 were the same as Example 4 except that the compositions of Examples 2 to 3 and the compositions of Comparative Examples 1 to 3 were used, respectively. A product was prepared. The obtained pressure-sensitive adhesive composition for labels was evaluated in the same manner as in Example 4. The results are shown in Table 3.

  From Tables 2 and 3, the following can be understood. That is, the pressure-sensitive adhesive composition for labels of the present invention is based on the block copolymer composition of the present invention, which exhibits low breaking strength and elongation at break, has good holding power, and has adhesive performance. It turns out that it is what was excellent in both die-cutting performance (Examples 4-6). On the other hand, in the adhesive composition for labels which does not contain the block copolymer composition of this invention, it is inferior to the performance balance of the said physical property (Comparative Examples 4-6).

According to the present invention, in order to obtain an adhesive composition excellent in both adhesive performance and die cutting performance when used in an adhesive label, it has excellent initial adhesive strength at low temperature and holding power at high temperature. A block copolymer composition is provided.
Since the pressure-sensitive adhesive composition has excellent pressure-sensitive adhesive performance over a wide temperature range, various pressure-sensitive adhesive tapes such as for packaging, office use, double-sided tape, masking and electrical insulation, pressure-sensitive adhesive sheets, pressure-sensitive labels, and dust removal rollers And particularly excellent in die cutting performance, it can be suitably used for adhesive labels.

Claims (7)

A block copolymer composition comprising an aromatic vinyl-isoprene-aromatic vinyl triblock copolymer (A) and an aromatic vinyl-isoprene block copolymer (B),
(I) Ratio (Mw _Da / Mw) of the weight average molecular weight Mw _{Da of the} polyisoprene block of the triblock copolymer (A) and the weight average molecular weight Mw _Db of the polyisoprene block of the diblock copolymer (B). _Db ) is 0.5 or more and less than 1,
(Ii) The proportion of the aromatic vinyl monomer unit in the entire polymer component contained is 10 to 30% by mass,
(Iii) A block copolymer composition having a breaking strength of less than 8 MPa and a breaking elongation of less than 1100%.   The block according to claim 1, wherein the weight average molecular weight of the triblock copolymer (A) is 100,000 to 250,000, and the weight average molecular weight of the diblock copolymer (B) is 100,000 to 300,000. Copolymer composition. The ratio between the content Ar ^b of the aromatic vinyl monomer unit of the the content Ar ^a aromatic vinyl monomer unit diblock copolymer (B) of the triblock copolymer (A) (Ar ^a / Ar ^b) is 1.5 or more claims 1 or 2 block copolymer composition.   The block copolymer composition in any one of Claims 1-3 which contains the said triblock copolymer (A) and the said diblock copolymer (B) in 20-80 mass%, respectively.   The adhesive composition containing the block copolymer composition and tackifying resin in any one of Claims 1-4.   The pressure-sensitive adhesive composition according to claim 5, which is used for a pressure-sensitive adhesive label.   The adhesive sheet which has an adhesive layer which consists of an adhesive composition of Claim 5.